Polymerization Of Vinyl Acetate Research Articles

Semi-continuous emulsion copolymerization of vinyl acetate and butyl acrylate in presence of AMPS

The emulsifier-free emulsion polymerization of vinyl acetate (VAc) and butyl acrylate (BA) in the presence of 2-acrylamido-2-methylpropane sulfonic acid (AMPS) was carried out by a semi-continuous process. AMPS was a reactive surfactant in the aqueous emulsion, due to its amphiphilic structure and the unsaturated double bonds. Potassium persulfate (KPS) was used as initiator. The following factors were mainly examined: quantity of AMPS, BA and KPS concentrations, which could significantly affect the particle size and its distribution, conversion, gel content, minimum film-forming temperature, etc. The particle size and its distribution were characterized by dynamic laser particle size analyzer, and morphology of the latex particles was characterized by transmission electron microscopy (TEM). Fourier transform infrared spectroscopy was used to characterize chemical structure of copolymers. The results indicated that AMPS was successfully reacted onto the resulted copolymer of vinyl acetate and butyl acrylate. A hydrophilic sulfonic acid group in the molecular structure of AMPS tended to be distributed in particles surface after polymerization. As a result, an electrostatic repulsion between the particles was produced in order to maintain stability of the system. Thermogravimetric analysis curves suggested that as BA content increased, thermal stability of the polymer increased accordingly. The conversion-time plots with varying AMPS and initiator contents were obtained, which illustrated that the initiator concentration could greatly influence the polymerization rate and the final conversion. The TEM micrographs of the final emulsifier-free latex particles for P(VAc/BA/AMPS) system revealed small particle size in monodisperse polymer latex. The particles of the latex were measured as about 150 nm.

UV stability of polymeric binder films used in waterborne facade paints

The UV-stability study of four polymeric binders for water-borne paints, based on acrylic, styrene-acrylic, vinyl acetate and vinyl acetate-butyl acrylate (co)polymers is described. To the best of our knowledge the UV stability of this set of binders relevant to decorative industry is systematically compared for the first time. Thin films obtained from the respective latexes were irradiated with UV light (λ≥275nm) and analysed using electrokinetic potential (ζ-potential), FTIR ATR spectroscopy, SEM microscopy and differential scanning calorimetry (DSC). The films obtained from different latexes displayed distinct changes in their surface composition and response to UV-irradiation. Among the studied compositions, the vinyl acetate-based ones seem to be the least prone to UV-degradation in the absence of other components typically present in paint formulations. The analytical techniques employed in this study are shown to be complementary and provide information on different regions of the surface layer, depending on their effective probing depth. Especially, a combination of FTIR and ζ-potential measurements is shown useful to clarify the nature of the carbonyl groups formed during photodegradation.

Non-Destructive Determination of Ethylene Vinyl Acetate Cross-Linking in Photovoltaic (PV) Modules by Raman Spectroscopy

Vibrational spectroscopy was found to be a suitable method for the determination of the degree of cross-linking of ethylene vinyl acetate (EVA) polymers. Spectral changes in the Raman spectra of EVA with increasing lamination time (which equals increasing degree of cross-linking) were mainly detected in the CH vibrational regions, namely, in the relative intensities of the characteristic CH3 and CH2 bands. These spectral regions were chosen for a chemometric evaluation where a calibration was performed with the Raman spectra of reference EVA samples and the results obtained from corresponding thermal analysis (differential scanning calorimetry) and Soxhlet extraction data. These datasets were subsequently used to non-destructively determine the progress of cross-linking in EVA foils, embedded in various mini-modules by Raman microscopy. Thus, we could show that Raman spectroscopy is a highly interesting method for quality control in the production of photovoltaic (PV) modules. However, this approach is valid only for a given grade of EVA, meaning a demand for a new calibration when changing the supplier or the type of EVA used. In addition, the applicability of infrared spectroscopy for the determination of the degree of cross-linking was tested. A good correlation of the decrease in intensity of the characteristic cross-linker infrared bands with increasing progress of the cross-linking was found, as determined by reference methods. However, this analytical method requires taking samples of the EVA foils and is, thus, unsuitable for the non-destructive determination of the degree of cross-linking of the EVA encapsulated within a PV module.

Effects of gamma irradiation on the crystallization, thermal and mechanical properties of poly(l-lactic acid)/ethylene-co-vinyl acetate blends

Poly(l-lactic acid)/ethylene vinyl acetate polymer blends (PLLA/EVA) with various blend ratios were prepared through melt blending process. The structural-property behavior of the polymer blends before and after they had been exposed to gamma irradiation was investigated. The hydrolytic degradation was investigated. The interfacial interaction between PLLA and EVA was visualized by Mechanical testing and FTIR. The crystallization behaviors of the blends were investigated by Differential scanning calorimetry (DSC), and the thermal stability was studied by thermogravimetric analysis (TGA). The results show that the hydrolytic degradation rate of PLLA/EVA blend can be widely controlled by exposing the PLLA/EVA to gamma-irradiation and also by EVA content. In alkaline solution, the hydrolytic degradation rate of the blends exposed 100 kGy and whose EVA content is higher than 50 wt% was decelerated while the rate of the unirradiated blends whose EVA content is lower than 20 wt% was accelerated. The tensile strength and modulus of the PLLA–EVA blend were increased by increasing PLLA content in the polymer blends and irradiation dose. FTIR spectra showed that some modifications occurred, after they had been exposed to gamma irradiation. The crystallization behavior was studied with differential scanning calorimetry and the composition-dependent changed of degree of crystallinity (Xc) of the PLLA phase indicated that PLLA and EVA were immiscible over the composition range investigated. However, there is a sharp decrease in the crystallinity with increasing EVA and irradiation dose. The TGA thermograms showed that the irradiated blends were less thermally stable than the unirradiated blends, at higher temperatures, the opposite situation was seen.

Cobalt-mediated radical polymerization of vinyl acetate in an alumina column using suspended polyvinyl acetate

Suspended polyvinyl acetate (SPVAc) was used as a solid adsorbent in the controlled radical polymerization of vinyl acetate. Benzoyl peroxide (BPO), cobalt (II) acetylacetonate (Co(acac)2) and N, N-dimethylformamide (DMF) were used as initiator, catalyst and ligand, respectively. In the absence of SPVAc solid adsorbent, polymerization yield was 51.56 % (Mn = 31,400 g.mol−1, PDI = 1.65), in 195 min. In the presence of SPVAc, both polymerization rate and induction time increased and polymerization yield was 65.6 % (Mn = 89,400 g.mol−1, PDI = 1.47) in 210 min. Suspended polyvinyl acetate was used in the polymerization in a packed alumina column as a top layer. In this method the slow adsorption and desorption of cobalt complex by SPVAc, was followed by the controlled radical polymerization and the final separation step. In the separation step, the green cobalt catalyst was absorbed by the column and the clean polymer (PVAc) with a narrow molecular weight distribution was isolated.

Preparation and characterization of a novel nanocomposite particles via in situ emulsion polymerization of vinyl functionalized silica nanoparticles and vinyl acetate

A new class of poly(vinyl acetate) (PVAc)/silica nanocomposite particles was successfully prepared in aqueous solution through a facile synthetic process. First, vinyl functionalized silica nanoparticles (VFSs) were synthesized using one-step method in aqueous emulsion, and then the vinyl groups located on the surface of VFSs were used to induced in situ polymerization of vinyl acetate. Scanning electron microscopy (SEM) images showed that VFSs and PVAc/silica nanocomposite particles all revealed highly monodispersed and uniform spheres. Especially, PVAc/silica nanocomposite particles obtained from transmission electron microscopy images presented an obvious core–shell structure, and the thickness of PVAc shell grafting on the surface of VFSs core was about 17 nm. In addition, the influence of the hydrolyzed and condensed time of vinyl triethoxysilane on the size and size distribution of VFSs was also investigated. The results of dynamic light scattering and SEM analysis indicated that the size and size distribution of VFSs decreased gradually with the extension of the reaction time from 6 to 48 h. Moreover, the structures and thermal properties of the samples were characterized via FT-IR and heat-flow DSC–TG.

Reversible addition-fragmentation chain-transfer polymerization of vinyl monomers with N,N- dimethyldiselenocarbamates

A new range of selenium-based reversible addition-fragmentation chain-transfer (RAFT) agents is described and tested in the polymerization of styrene, acrylates, vinyl esters, and N-vinylcaprolactam. The synthesized N,N-dimethyldiselenocarbamates were poor control agents for styrene polymerization, whereas polyacrylates of controlled molar masses and bearing a diselenocarbamate terminal group could be synthesized. The polymerization of vinyl acetate and vinyl pivalate proceeded in a controlled manner as confirmed by size-exclusion chromatography, matrix-assisted laser desorption ionization-time-of-flight mass spectrometry, and 77Se NMR analyses. The capability of these RAFT agents to control the polymerization of both more-activated monomers and less-activated monomers was exemplified through the synthesis of a poly(t-butyl acrylate)-b-poly(vinyl acetate) diblock copolymer. Considering the very broad range of carbamate groups which can be envisioned, this finding opens numerous perspectives for diselenocarbamate-mediated RAFT polymerization with its specificities yet to be explored. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4361–4368

Controllable synthesis of a novel poly(vinyl alcohol)-based hydrogel containing lactate and PEG moieties

Tunable hydrogel that contained well-defined poly(vinyl alcohol) (PVA), labile lactate groups, and hydrophilic poly(ethylene glycol) (PEG) segments was prepared through a combination of reversible addition-fragmentation chain transfer (RAFT) polymerization and esterification reaction. A diol was prepared via the esterification between lactic acid (LA) and PEG. Then the diol was allowed to react with maleic anhydride to produce a diacid. Meanwhile, well-defined PVA was synthesized by the alcoholysis of poly(vinyl acetate) (PVAc) obtained by RAFT polymerization of vinyl acetate. The hydrogels with tailor-made structure were generated by crosslinking PVA with LA-based diacid. The structures and properties of LA-based intermediates and the hydrogels were characterized with Fourier transform infrared spectroscopy, gel permeation chromatography, differential scanning calorimetry, and thermogravimetric analysis. Both LA-based diol and diacid were semicrystalline and water-soluble, their melting temperature and glass transition temperature were 52 and −51, 54 and −41°C, respectively. The polydispersity indexes of the precursor of PVA samples were within the range of 1.03–1.10. It was found that the thermal stability of hydrogel was higher than that of LA-based diacid. Both the swelling and release properties of the hydrogels depend on the feeding ratio of PVA/LEM and the chain length of PVA, which reflected that the structure and properties of the hydrogels were controllable. POLYM. ENG. SCI., 54:1366–1371, 2014. © 2013 Society of Plastics Engineers

The modification of bitumen with reactive ethylene terpolymer, styrene butadiene styrene and variable amounts of ethylene vinyl acetate

In this article, 50/70 penetration graded TUPRAS bitumen was modified. Reactive elastomeric terpolymer (Elvaloy RET) from DuPont, ethylene vinyl acetate (EVA) and styrene butadiene styrene (SBS) polymers were used in the bitumen modification. Set hours of the tests were applied to samples taken from the obtained modified bitumen mixture, and 1 % reactive ethylene terpolymer, 1 % SBS and 0.5, 1, 1, 5, 2, and 2.5 % EVA (w/w) were added to the raw bitumen. Penetration, penetration index, softening point, ductility and % elastic recovery tests were performed with the modified bitumen and raw bitumen. The samples of raw bitumen and modified bitumen with 2 % RET, 1 % SBS and 1 % EVA were investigated by means of IR spectroscopy (FT-IR) and thermogravimetrical analysis/differential thermal analysis (TG/DTA). The raw bitumen was modified with RET, SBS and EVA, and it was determined that the penetration and ductility values were decreased while the penetration index, softening point and % elastic recovery were increased. The most important characteristics (such as softening point, penetration and % elastic recovery) of the new polymer-modified bitumen (NPMB) containing 2.5 % EVA, 1 % RET and 1 % SBS were compared with eight different types of polymer-modified bitumens in Turkey (TPMB). NPMB provided all the required parameters (softening point, penetration and % elastic recovery) for two different types of TPMBs (TPMB 70-16, TPMB 70-22).

Organometallic mediated radical polymerization of vinyl acetate with Fe(acac)2

The radical polymerization of vinyl acetate (VAc) is moderated by iron(II) acetylacetonate (Fe(acac)2) by the organometallic route (OMRP), as well as by degenerative transfer polymerization (DTP) when in the presence of excess radicals, through the formation of thermally labile organometallic FeIII dormant species. The poly(vinyl acetate) (PVAc)-FeIII(acac)2 dormant species has been isolated in the form of an oligomer and characterized by 1H NMR, EPR, and IR methods, and then used as a single-component initiator for the OMRP of VAc. The degree of polymerization of this isolated oligomeric species demonstrates the limited ability of Fe(acac)2, relative to the Co(acac)2 congener, to rapidly trap the growing PVAc radical chain. Control under OMRP conditions is improved by the presence of Lewis bases, especially PMe2Ph. On the other hand, iron(II) phthalocyanine inhibits the radical polymerization of VAc completely. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3494–3504

Soft-Sensing Modeling Method of Vinyl Acetate Polymerization Rate

In the procedure of polyvinyl alcohol production, it is hardly accurate measuring the Vinyl Acetate (VAC) polymerization rate. To solve this awkward situation, this paper adopt Genetic Algorithm-Back Propagation (GA-BP) Neural Network to fit the nonlinear relation of the variables which derives from the production process by setting the VAC polymerization rate as the master variable and the initiator addition ratio, methanol ratio, polymerization temperature and VAC activity degree as auxiliary variables. Establish VAC polymerization rate soft-sensing model based on GA-BP network which the connection weights optimized by genetic algorithm. The comparison results with BP network based on the actual measured data show that the model this paper constructed is accurate and effective. DOI: http://dx.doi.org/10.11591/telkomnika.v11i6.2724 Full Text: PDF

Influence of Zeolite Additive on the Properties of Plaster Used for External Walls from Autoclaved Aerated Concrete

Enclosures that had been built from elements of autoclaved aerated concrete (AAC) often are covered with plasters. Some adhesion problems between plasters and surface exist during the mechanized covering of surfaces of the mentioned enclosures with plaster. Some dispersible additives (vinyl acetate polymer or derivatives of acrylic acid esters) are used to improve the adhesion. Another problem is the increased water absorption of AAC elements, therefore water retarding additives (cellulose esters) are used in the mixture of plasters. Due to insufficient amount of water in the mixture of plasters, the hydration of cement minerals slows down. Influence of the natural zeolite – clinoptilolite on the properties of plaster is analyzed in this work. It was found that this additive effectively absorbs water and thus, ensures adequate hydration of cement minerals. When in the mixture of plaster the sand is changed by clinoptilolite in amount of 15 % the structure slightly compacts, the compressive and flexural strength of hardened plaster increase by 47 % and 12 % respectively and the adhesion to a surface of the AAC element increases by 44 %. Drying shrinkage, water vapor resistance factor and coefficient of capillary absorption remain unchanged.DOI: http://dx.doi.org/10.5755/j01.ms.19.2.4441

Effect of Head-to-Head Addition in Vinyl Acetate Controlled Radical Polymerization: Why Is Co(acac)2-Mediated Polymerization so Much Better?

The controlled polymerization of vinyl acetate has been recently achieved by several techniques, but PVAc with targeted Mn and low dispersity up to very high monomer conversions and high degrees of polymerization was only obtained with Co(acac)2 as controlling agent in the so-called CMRP, a type of organometallic mediated radical polymerization (OMRP). Other techniques (including ATRP, ITP, TERP, and RAFT/MADIX) have shown a more or less pronounced slowdown in the polymerization kinetics, which was attributed to the higher strength of the C–X bond between the radical PVAc chain and the trapping agent (X) in the dormant species and to a consequent slower reactivation after a less frequent head-to-head monomer addition. The reason for the CMRP exception is clarified by the present contribution. First, a detailed investigation by 1H, 13C and multiplicity-edited HSQC and DEPT-135 NMR of the PVAc obtained by CMRP, in comparison with a regular polymer made by free radical polymerization under the same condition...

Novel supramolecular block copolymer containing organic–inorganic pentablock copolymer by ATRP of styrene and vinyl acetate using polydimethylsiloxane/cyclodextrin inclusion complexes as macroinitiator

Organic–inorganic pentablock copolymers have been synthesized via atom transfer radical polymerization (ATRP) of styrene (St) and vinyl acetate (VAc) monomers at 60 °C using CuCl/N,N,N′,N″,N″-pentamethyldiethylenetriamine as a catalyst system initiated from boromoalkyl-terminated poly(dimethylsiloxane) (PDMS)/cyclodextrins macroinitiator (Br-PDMS/γ-CD). Br-PDMS-Br was reacted with γ-CD in different conditions with inclusion complexes being characterized through hydrogen nuclear magnetic resonance (1H NMR) and differential scanning calorimetry (DSC). Resulting Br-PDMS-Br/γ-CD inclusion complexes were taken as macroinitiators for ATRP of St and VAc. Well-defined poly(styrene)-b-poly(vinyl acetate)-b-poly(dimethylsiloxane/γ-cyclodextrin)-b-poly(vinyl acetate)-b-poly(styrene) (PSt-b-PVAc-b-PDMS/γ-CD-b-PVAc-b-PSt) pentablock copolymer was characterized by 1H NMR, gel permeation chromatograph (GPC) and DSC. There was a good agreement between the number-average molecular weight calculated from 1H NMR spectra and that of theoretically calculated. Pentablock copolymers consisting of Br-PDMS-Br/γ-CD inclusion complex as central blocks (inorganic block) and PVAc and PSt as terminal blocks were synthesized by this technique. PSt-b-PVAc-b-PDMS/γ-CD-b-PVAc-b-PSt pentablock copolymer can undergo a temperature-induced reversible transition upon heating of the copolymer complex from white complex at 22 °C to green complex in 55 °C which characterized with XRD and 1H NMR. XRD showed a change in crystallinity percent of St peak with changing the temperature which calculated by Origin75 software.

Organoboranes-atmospheric oxygen systems as unconventional initiators of radical polymerization

This paper provides the first generalization and analysis of our results and published data about a new type of pseudoliving process: radical polymerization mediated by boroxyl radicals generated through the oxidation of organoboranes by atmospheric oxygen. The kinetics and mechanism of polymerization of methyl methacrylate and vinyl acetate in the presence of ammonia-organoboranes and boracyclanes are studied. Methods of practical use of polymerization initiated by organoborane-oxygen systems for macromolecular design are discussed.

Novel high porosity mesoporous silica using new mixed two‐block copolymers as a template

ABSTRACTMixed block copolymers have been used as a template in the synthesis of new mesoporous silica particles, prepared from sol–gel method. The prominent effect of the block copolymers have been used to provide a new template that controls the surface area and porosity of the particles. Tetraethyl orthosilicate as silica source and two block copolymers, poly(propylene oxide)‐b‐poly(ethylene oxide)‐b‐poly(propylene oxide) and poly(ethylene oxide)‐b‐poly(propylene oxide)‐b‐poly(ethylene oxide) (Pluronics) as a surfactant, were used in water/n‐octane co‐solvent with citric acid catalyst to prepare new nanostructures of mesoporous silica (SPB1 and SPB1,2). The displacement of ethanol with cyclohexanol as a co‐surfactant drastically changed the surface properties of the new mesoporous silica particles (SPB1,2). The surface area, porosity, morphology, and microstructure of particles were characterized by X‐ray diffraction, nitrogen adsorption–desorption, scanning electron microscopy), and transmission electron microscopy. The prepared particles have been specifically characterized for specific use and applications as supporting catalysts for the polymerization of vinyl acetate, drugs delivery, and in the membranes manufacturing based on polyurethanes. © 2013 Curtin University of Technology and John Wiley & Sons, Ltd.

Seleno‐containing poly(vinyl acetate) prepared by diselenocarbonates‐mediated controlled free radical polymerizations

ABSTRACTThe living free radical polymerizations of vinyl acetate (VAc) were successfully achieved in the presence of a novel organic selenium compound (diselenocarbonates), with 2,2′‐azobisisobutyronitrile (AIBN) as the initiator. The living characteristics of the VAc polymerization were confirmed by the linear first‐order kinetic plots and linear increase of molecular weights (Mn) of the polymers with monomer conversions, while keeping the relatively low molecular weight distributions. In addition, the end of the polymers contains selenium element which may be useful in biotechnological and biomedical applications. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3159–3165

Abstract 3211: Proteomic analysis of nuclei dissected from FFPE tissue using expression microdissection.

Abstract Currently, proteomic analysis of formalin-fixed, paraffin-embedded (FFPE) tissue (the most common method of storing tissue specimens) are limited by the overwhelming complexity of the cellular proteome, which makes disease related changes in protein expression difficult to detect. Expression Microdissection (xMD) allows for automated, operator-independent dissection of specific cells or subcellular organelles in FFPE tissue, resulting in the enrichment of specific, selectable protein populations. In xMD, tissue slices that have been stained for specific cellular markers using immunohistochemical (HC) methods are placed under a layer of ethylene vinyl acetate (EVA) polymer film. When the stack is uniformly illuminated (using a rastering laser or a light pulse), the EVA melts and makes contact only over the stained tissue, enabling specific capture and transfer of these areas for further biochemical analysis, while leaving unstained tissue behind. As a proof of principle, we are using the xMD technique to enrich for nuclei in FFPE rat brain tissue sections followed by proteomic analysis. Shotgun proteomic analysis of these samples show a significant enrichment in nuclear localized proteins, with an average 18% of recovered proteins localized to the nucleus-versus 11% of recovered proteins in whole tissue scrapes. Targeted mass spectrometry, using Multiple Reaction Monitoring (MRM), also shows an enrichment of nuclear markers such as histones and DNA-binding proteins, and a de-enrichment of non-nuclear proteins. The enrichment for nuclei allows for the identification of methylated lysines on histones that are not detected in whole tissue scrapes, most likely due to their low abundance. The evolving methodology may allow researchers to profile the sub-cellular proteome of patient samples to identify potential new disease biomarkers and drug targets. This novel technology could also be used to advance our understanding of the biomolecular changes responsible for a specific disease state. Citation Format: Adele R. Blackler, Michael A. Tangrea, Tom Pohida, Nicole Morgan, Robert Bonner, Keshia Mora, John Kakareka, Sanford Markey, Michael R. Emmert-Buck. Proteomic analysis of nuclei dissected from FFPE tissue using expression microdissection. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3211. doi:10.1158/1538-7445.AM2013-3211

Durability of Polymer Modified Repair Mortars on Concrete Structures

Polymer modified mortars (PMM) used as repair products present higher intrinsic properties than classic mortar due to polymer effect in the cementitious matrix. But evolution of their adhesives properties is not well known. This article deals with adhesive behavior of two PMMs made in laboratory with styrene acrylate (SA) and ethylene vinyl acetate (EVA) polymers. It is highlighted that adhesion of these mortars depends on polymer amount in the mortar, on the environmental conditions, and on the roughness of the concrete support. This adhesion is improved in warm environment and with high roughness of support surface. The influence of polymer amount is not the same for the two types of polymers but in the two cases, bond strength remains low when low amount of polymer are added.

Kinetic Modeling of Radical Thiol–Ene Chemistry for Macromolecular Design: Importance of Side Reactions and Diffusional Limitations

The radical thiol–ene coupling of thiol-functionalized polystyrene (PS-SH) with dodecyl vinyl ether (DVE) and the polystyrene-b-poly(vinyl acetate) (PS-b-PVAc) polymer–polymer conjugation using 2,2-dimethoxy-2-phenylacetophenone (DMPA) as photoinitiator are modeled to assess the importance of diffusional limitations and side reactions. Intrinsic chemical rate coefficients are determined based on a kinetic study of the coupling of benzyl thiol (BT) and DVE. The addition and transfer reactions are chemically controlled, whereas diffusional limitations on termination slightly increase the coupling efficiency. Termination by recombination of carbon-centered radicals and addition of DMPA derived radicals to DVE are shown to be mainly responsible for the reduced coupling efficiency in case polymeric species are involved. The obtained results confirm the idea to disregard radical thiol–ene chemistry as a true member of the family of “click” chemistry techniques for polymer–polymer conjugation and show that the initial conditions have a significant impact on the coupling efficiency.